1. What are germs?
2. Getting germs
3. Germ environment
4. Germ travel
6. Water's role
7. Water suppliers
Diseases & pathogens
Note on E. coli
is water's role?
Under the proper (or rather, improper) conditions, drinking water can provide the link between hosts. An infected individual excretes millions of pathogenic microbes daily, and some of those may find their way into lakes or streams. If other people drink the contaminated water while the microbes are still viable, alive and able to reproduce, more people become infected. If each new case of infection produces ten more cases, the number of sick people increases exponentially (from one to ten to a hundred to a thousand). Such an event is an epidemic, rapid and extensive spread of infection among individuals.
Effective sanitation stops the cycleThe fecal-oral route, from the end of one digestive tract to the beginning of another, can be interrupted by adequate sanitation. Sanitation refers primarily to wastewater and sewage treatment of human waste, but it also refers to systems that treat water between its source in nature and the consumer. The role of wastewater treatment is to collect and process human waste to stop the transmission of pathogens by killing them. Areas with poor sanitation are fertile ground for the spread of disease. Even where sanitation is in place, it can be disrupted by natural events, such as storms or earthquakes, or human events, such as wars, making populations vulnerable to epidemic.
Surface Water versus Groundwater
MWRA uses surface water collected in reservoirs as its drinking water supply. Other surface water sources include rivers, streams, lakes or ponds. The alternative to surface water is groundwater obtained from wells. Most large cities in the United States rely on surface water, while many smaller towns or individual homes depend on wells. These two sources are quite different with regard to biological contamination. Surface water is almost certain to carry some bacteria; groundwater from properly constructed and maintained wells is almost certain to be free of them. Rain may encounter animal waste on the surface, but as it seeps into the ground, microbes are filtered out by soils, sand and gravel before the water reaches the water table. When it is pumped to the surface, it has undergone nature's filtration.
Surface water is never contaminant free
people who drink the water certain to get sick? Not at all. Depending
on the pathogen, if only one or two such microbes are ingested, hopefully
the body's immune system will identify and defeat the invader. If a few
more microbes are ingested, that might make some people sick. In other
words, if everyone in a group swallows the same dose, some people may
get sick while others do not. Despite all the "maybes," one fact is certain:
the higher the concentration of pathogens in the water, the more people
are likely to get sick.
Water and wild animals
Do wild animals ever get sick by drinking from rivers and ponds?
There are several answers to this question: